The present invention relates to a variable venturi type carburetor provided with a partition plate formed at the bottom of the suction piston, in order to prevent the self-exciting oscillation of the suction piston.
Such a variable venturi type carburetor has been known as having a partition plate disposed at the bottom of the suction piston, such that the increment of the venturi opening area in relation to the displacement of the suction piston is gradually increased. This type of carburetor can effectively avoid the self-excited vibration of the suction piston without necessitating a damper means such as a hydraulic damper. In this type of carburetor, however, it is necessary to control and manage and gap between the partition plate and the bridge formed on the carburetor body opposing to the partition plate, for otherwise the intake air flowing through this gap will be changed to cause a change in the displacement of the suction piston, i.e. a change in the projection area of the venturi opening, resulting in a fluctuation of operation of the carburetor.
Namely, the relative position between the metering needle attached to the suction piston and the main jet fixed to the carburetor barrel fluctuates even for a constant intake air flow rate, resulting in a variation of the fuel metering area which would deteriorate the precision of control of fuel flow.